Diaphragm pump

ABSTRACT

A diaphragm pump includes a diaphragm, a diaphragm case and a driver. The diaphragm has a center point and an outer peripheral portion. The diaphragm case supports the diaphragm at the outer peripheral portion thereof, thereby defining a pump chamber in the diaphragm case. The driver holds the diaphragm at the center point thereof. The diaphragm is deformed as the driver is reciprocated, thereby accomplishing a fluid to flow into and to be discharged out of the pump chamber. The driver includes a fitting member and a flange. The fitting member fits the diaphragm and has a first surface for contacting the diaphragm. The flange is formed outside the fitting member. The flange has a second surface for contacting the diaphragm when the diaphragm is deformed toward the pump chamber. The second surface has a first convex surface region which is formed continuously with the first surface.

BACKGROUND OF THE INVENTION

The present invention relates to a diaphragm pump.

Japanese Unexamined Utility Model Publication No. 7-14179 discloses the diaphragm pump. As shown in FIG. 3, a diaphragm 92 is supported at an outer peripheral portion 92 a thereof by a fixing surface (a joint surface) 91 a of a diaphragm case 91. The diaphragm case 91 and the diaphragm 92 have defined a pump chamber 93 in the diaphragm case 91. The diaphragm 92 has fitted at the center thereof a driver (a rod) 94 which is driven so as to reciprocate by a drive source such as an electric motor (not shown). As the reciprocation of the driver 94 causes the deformation (displacement) of the diaphragm 92, the volume of the pump chamber 93 is increased and decreased, thereby allowing a fluid to flow into and to be discharged out of the pump chamber 93.

In the diaphragm pump, when the pressure in the pump chamber 93 rises in a discharge stroke, while a part of the diaphragm 92 which the driver 94 contacts is supported by the driver 94, the outside part of the diaphragm 92 which the driver 94 does not contact is not directly supported by the driver 94 and is generally expanded toward the opposite side to the pump chamber 93. Since even in the last stage of the discharge stroke, the volume of the pump chamber 93 is not sufficiently reduced, the fluid which is not discharged from the pump chamber 93 and remains in the pump chamber 93 is increased, with the result that the pump efficiency of the diaphragm pump deteriorates.

In the diaphragm pump, however, the driver 94 includes a fitting member 95 which fits the diaphragm 92 and a flange 96 which is formed on the outside part of the fitting member 95. The flange 96 is contacted with the diaphragm 92 when the diaphragm 92 is deformed toward the pump chamber 93, thereby preventing the outside part of the diaphragm 92 from expanding toward the opposite side to the pump chamber 93 in the discharge stroke.

In the driver 94 of the diaphragm pump shown in FIG. 3, however, since a surface 95 a of the fitting member 95 which contacts the diaphragm 92 is not formed continuously with a surface 96 a of the flange 96 which contacts the diaphragm 92, a boundary between the surface 95 a and the surface 96 a is angled. Therefore, the diaphragm 92 deformed in the discharge stroke contacts the angled boundary at an angle of deflection, thereby reducing the durability of the diaphragm 92.

SUMMARY OF THE INVENTION

The present invention is directed to a diaphragm pump which improves durability of a diaphragm while maintaining high pump efficiency.

The present invention provides the following feature. A diaphragm pump includes a diaphragm, a diaphragm case and a driver. The diaphragm has a center point and an outer peripheral portion. The diaphragm case supports the diaphragm at the outer peripheral portion thereof, thereby defining a pump chamber in the diaphragm case. The driver holds the diaphragm at the center point thereof. The diaphragm is deformed as the driver is reciprocated, thereby accomplishing a fluid to flow into and to be discharged out of the pump chamber. The driver includes a fitting member and a flange. The fitting member fits the diaphragm and has a first surface for contacting the diaphragm. The flange is formed outside the fitting member. The flange has a second surface for contacting the diaphragm when the diaphragm is deformed toward the pump chamber. The second surface of the flange has a first convex surface region which is formed continuously with the first surface of the fitting member.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments, together with the accompanying drawings, in which:

FIG. 1 is a sectional view illustrating a diaphragm pump according to a preferred embodiment of the present invention;

FIG. 2 is a sectional view illustrating a diaphragm pump according to another preferred embodiment of the present invention; and

FIG. 3 is a sectional view illustrating a prior art diaphragm pump.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A diaphragm pump according to a preferred embodiment of the present invention will now be described with reference to FIG. 1. In the present preferred embodiment, the diaphragm pump is adapted for feeding gas.

FIG. 1 shows a sectional view illustrating a diaphragm pump. As shown in FIG. 1, the diaphragm pump has a diaphragm case 10 which includes a block 11, a circular tension plate 12 which is fixedly joined to the block 11, and a body case 13 in which the block 11 and the tension plate 12 are accommodated. The body case 13 is formed in a cylindrical cover shape with the cover portion thereof located on the upside as seen in FIG. 1. The block 11 and the tension plate 12 are received in the body case 13 such that the block 11 is located on the cover side.

The block 11 has formed in the end surface thereof facing the tension plate 12 a concave portion 11 a. The concave portion 11 a is closed by the diaphragm 14 which is interposed between the block 11 and the tension plate 12, thereby defining a pump chamber 15. The diaphragm 14 is made of metallic material and has a circular shape. The block 11 and the tension plate 12 support the diaphragm 14 so as to permit the deformation (displacement) of the diaphragm 14 by holding an annular region of an outer peripheral portion 14 a of the diaphragm 14 at the joints of the block 11 and the tension plate 12, or between a fixing surface 31 of the block 11 and a fixing surface 36 of the tension plate 12 which faces the fixing surface 31.

The body case 13 has formed therein a suction passage 17 to which an external low-pressure piping (not shown) is connected, and a discharge passage 18 to which an external high-pressure piping (not shown) is connected. The block 11 has formed in the middle thereof a suction port 25 which connects the pump chamber 15 to the suction passage 17, and a discharge port 26 which connects the pump chamber 15 to the discharge passage 18. A suction valve 21 in the form of a reed valve is provided between the suction port 25 in the block 11 and the suction passage 17 in the body case 13. A discharge valve 22 in the form of a reed valve is provided between the discharge port 26 in the block 11 and the discharge passage 18 in the body case 13.

To the diaphragm 14 is connected a drive unit 24 which drives the diaphragm 14. The drive unit 24 is formed with a rod 45 functioning as a driver which is driven so as to reciprocate by a drive source such as an electric motor (not shown). The rod 45 holds the diaphragm 14 at the center point thereof between a fitting member 46 which is arranged outside the pump chamber 15 and fits the diaphragm 14 and a fixing member 47 which is arranged inside the pump chamber 15 and fixed to the fitting member 46. Therefore, the diaphragm 14 is deformed (displaced) as the rod 45 is reciprocated, thereby increasing and decreasing the volume of the pump chamber 15.

Specifically, when the rod 45 is moved in a direction in which the rod 45 leaves the pump chamber 15 (downward in FIG. 1), the diaphragm 14 is deformed toward the opposite side to the pump chamber 15 and the volume of the pump chamber 15 is increased. During a suction process when the diaphragm 14 is deformed toward the opposite side to the pump chamber 15, gas is introduced from the suction passage 17 to the pump chamber 15 while pushing open the suction valve 21. In contrast, when the rod 45 is moved toward the pump chamber 15 (upward in FIG. 1), the diaphragm 14 is deformed toward the pump chamber 15 and the volume of the pump chamber 15 is decreased. During a discharge process when the diaphragm 14 is deformed toward the pump chamber 15, the gas in the pump chamber 15 is discharged to the discharge passage 18 while pushing open the discharge valve 22.

The rod 45 includes the fitting member 46 and a circular flange 49 outside the fitting member 46. The flange 49 is contacted with the diaphragm 14 when the diaphragm 14 is deformed toward the pump chamber 15, thereby preventing the outside part of the diaphragm 14 from expanding toward the opposite side to the pump chamber 15 in a discharge stroke. Since even in the last stage of the discharge stroke, the volume of the pump chamber 15 is sufficiently reduced, the fluid which is not discharged from the pump chamber 15 and remains in the pump chamber 15 is decreased, with the result that the pump efficiency of the diaphragm pump is improved.

A surface 49 a of the flange 49 contacting the diaphragm 14 has a convex surface region 51 which is formed continuously with a surface 46 a (plane) of the fitting member 46 contacting the diaphragm 14 so as to form no angle. Therefore, in a case where the diaphragm 14 is deformed toward the pump chamber 15, even when the diaphragm 14 contacts the vicinity of a boundary between the contacting surface 46 a of the fitting member 46 and the contacting surface 49 a of the flange 49, the convex surface region 51 will have no angle of deflection, so that the durability of the diaphragm 14 is improved.

The contacting surface 49 a of the flange 49 has a concave surface region 52 in addition to the aforementioned convex surface region 51. The convex surface region 51 contacts the diaphragm 14 at a portion of the convex surface region 51 adjacent to the fitting member 46 in an annular region. The concave surface region 52 is formed continuously with the convex surface region 51 and contacts the diaphragm 14 at a portion of the concave surface region 52 adjacent to the outer peripheral portion 14 a in an annular region.

As shown in FIG. 2, in a case where the contacting surface 49 a of the flange 49 is formed only by the convex surface region, when the diaphragm 14 is deformed toward the pump chamber 15 with a relatively great curvature radius, a part of the diaphragm 14 adjacent to the outer peripheral portion 14 a is bent with a relatively great curvature radius at a portion of the diaphragm 14 which is not supported by the contacting surface 49 a of the flange 49, such that the part of the diaphragm 14 is interposed between the contacting surface 49 a and the fixing surface 31. In the diaphragm 14 shown by chain double-dashed line in FIG. 2, the portion of the diaphragm 14 is indicated by an arrow “M”.

In the present embodiment, when the diaphragm 14 is deformed toward the pump chamber 15 with a relatively great curvature radius, however, the part of the diaphragm 14 adjacent to the outer peripheral portion 14 a is bent so as to conform with the contacting surface 49 a of the flange 49 (or the concave surface region 52), that is, the part of the diaphragm 14 is bent in such a state that the part of the diaphragm 14 is supported by the contacting surface 49 a, such that the part of the diaphragm 14 is interposed between the contacting surface 49 a and the fixing surface 31. Such a structure prevents the diaphragm 14 from being bent with a relatively great curvature radius at the portion of the diaphragm 14 which is not supported by the contacting surface 49 a of the flange 49, with the result that the durability of the diaphragm 14 is improved.

The curvatures of the convex surface region 51 and the concave surface region 52 of the contacting surface 49 a of the flange 49 are the same. To be more specific, a curvature radius R1 of a curved line X1 for the convex surface region 51 and a curvature radius R2 of a curved line X2 for the concave surface region 52 as viewed on a plane which extends perpendicularly to the diaphragm 14 in its flat position and passes through a center point P of the diaphragm 14 (i.e. the plane of the drawing of FIG. 1), are the same.

Therefore, when the diaphragm 14 is deformed with a relatively great curvature radius toward the pump chamber 15, a part of the diaphragm 14 contacting either one of the convex surface region 51 and the concave surface region 52 of the flange 49 is prevented from being bent with a greater curvature radius than the other part of the diaphragm 14, thereby preventing stress caused by bending moment from being applied unevenly to the diaphragm 14 which is in contact with the contacting surface 49 a of the flange 49. Consequently, the durability of the diaphragm 14 is further improved.

The block 11 has formed a saving recess 48 in the middle of the inner surface of the pump chamber 15. The saving recess 48 accommodates the fixing member 47 which fixes the rod 45 when the diaphragm 14 deformed toward the pump chamber 15 is located at the top dead center thereof where the volume of the pump chamber 15 is minimized as shown by chain double-dashed line in FIG. 1. The inner surface of the pump chamber 15 of the block 11 other than the saving recess 48 forms a regulating surface 32 which provides a limit of deformation of the diaphragm 14 toward the top dead center thereof. That is, when the diaphragm 14 deformed toward the pump chamber 15 is located at the top dead center, the surface of the diaphragm 14 which faces the fluid chamber 15 is brought into contact with the regulating surface 32, thereby preventing the diaphragm 14 from being further elastically deformed.

The regulating surface 32 is shaped so as to conform with the contacting surface 49 a of the flange 49. Therefore, in a state where the diaphragm 14 is located at the top dead center thereof, the diaphragm 14 is sandwiched substantially between the entirety of the contacting surface 49 a of the rod 45 (the flange 49) and the entirety of the regulating surface 32 of the block 11, and the volume of the pump chamber 15 becomes substantially zero, accordingly, thus further improving the pump efficiency of the diaphragm pump.

Specifically, the regulating surface 32 includes a convex surface region 33 which is shaped so as to conform with the concave surface region 52 of the contacting surface 49 a of the flange 49 and a concave surface region 34 which is shaped so as to conform with the convex surface region 51 of the contacting surface 49 a. The convex surface region 33 is formed smoothly continuously with the fixing surface 31 such that the boundary therebetween forms no angle. The convex surface region 33 supports the diaphragm 14 which is located at the limit of deformation toward the top dead center thereof at a portion of the convex surface region 33 adjacent to the outer peripheral portion 14 a in an annular region. The concave surface region 34 is formed smoothly continuously with the convex surface region 33 such that the boundary therebetween forms no angle. The concave surface region 34 supports the diaphragm 14 which is located at the limit of deformation toward the top dead center thereof at a portion of the concave surface region 34 adjacent to the center point P of the diaphragm 14 in an annular region.

Therefore, even when the diaphragm 14 is located at the limit of its deformation toward the top dead center thereof and shaped to conform with the regulating surface 32, the vicinities of the boundaries between the fixing surface 31 and the regulating surface 32 and between the convex surface region 33 and the concave surface region 34 will have no angle of deflection, so that plastic deformation of the diaphragm 14 caused by deflection is prevented and reduction of the durability of the diaphragm 14 is prevented, accordingly.

The curvatures of the convex surface region 33 and the concave surface region 34 are the same. In addition, the curvatures of the convex surface region 33 and the concave surface region 34 are the same as those of the convex surface region 51 and the concave surface region 52. To be more specific, the curvature radius R1, the curvature radius R2, a curvature radius R3 of a curved line X3 for the convex surface region 33 and a curvature radius R4 of a curved line X4 for the concave surface region 34 as viewed on a plane which extends perpendicularly to the diaphragm 14 in its flat position and passes through the center point P of the diaphragm 14 (i.e. the plane of the drawing of FIG. 1), are the same.

Therefore, when the diaphragm 14 is located at the limit of its deformation toward the top dead center thereof, the curvatures of the parts of the diaphragm 14 interposed between the convex surface region 33 of the regulating surface 32 and the concave surface region 52 of the flange 49 and between the concave surface region 34 of the regulating surface 32 and the convex surface region 51 of the flange 49 are prevented from being different, thereby preventing stress caused by bending moment from being applied unevenly to the diaphragm 14 which is located at the limit of its deformation toward the top dead center thereof. Consequently, the durability of the diaphragm 14 is further improved.

It is noted that the following embodiments are also practicable without departing from the purpose of the invention.

As shown in FIG. 2, the contacting surface 49 a of the flange 49 of the rod 45 is formed only by a convex surface region. In addition, the regulating surface 32 of the diaphragm case 10 (or the block 11) is formed only by a concave surface region so as to be shaped to conform with the contacting surface 49 a of the flange 49, which is formed only by the convex surface region.

In an alternative embodiment to the preferred embodiment, the curvatures of the convex surface region 51 and the concave surface region 52 of the contacting surface 49 a of the flange 49 are differentiated from each other. In another alternative embodiment to the preferred embodiment, the curvatures of the convex surface region 33 and the concave surface region 34 of the regulating surface 32 are differentiated from each other. In a case where the former and latter alternative embodiments are combined, if the curvature of the concave surface region 34 of the regulating surface 32 is the same as that of the convex surface region 51 of the flange 49, and if the curvature of the convex surface region 33 of the regulating surface 32 is the same as that of the concave surface region 52 of the flange 49, the regulating surface 32 is shaped so as to conform with the contacting surface 49 a of the flange 49.

Although, in the above-mentioned embodiment the diaphragm pump of the present invention is applied to the diaphragm pump for handling the gas, the diaphragm pump of the present invention is not limited to such diaphragm pump, but it is applicable to a diaphragm pump for handling a liquid.

Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein but may be modified. 

1. A diaphragm pump comprising: a diaphragm having a center point and an outer peripheral portion; a diaphragm case for supporting the diaphragm at the outer peripheral portion thereof, thereby defining a pump chamber in the diaphragm case; a driver for holding the diaphragm at the center point thereof, the diaphragm being deformed as the driver is reciprocated, thereby accomplishing a fluid to flow into and to be discharged out of the pump chamber, the driver comprising: a fitting member for fitting the diaphragm, the fitting member having a first surface for contacting the diaphragm; and a flange formed outside the fitting member, the flange having a second surface for contacting the diaphragm when the diaphragm is deformed toward the pump chamber, wherein the second surface of the flange has a first convex surface region which is formed continuously with the first surface of the fitting member.
 2. The diaphragm pump according to claim 1, wherein the second surface of the flange has a first concave surface region in addition to the first convex surface region, the first convex surface region contacting the diaphragm at a portion of the first convex surface region adjacent to the fitting member, the first concave surface region being formed continuously with the first convex surface region, the first concave surface region contacting the diaphragm at a portion of the first concave surface region adjacent to the outer peripheral portion of the diaphragm.
 3. The diaphragm pump according to claim 2, wherein curvatures of the first convex surface region and the first concave surface region of the second surface of the flange are the same.
 4. The diaphragm pump according to claim 1, wherein the diaphragm case has a regulating surface which forms an inner surface of the pump chamber and is shaped so as to conform with the second surface of the flange, thereby providing a limit of deformation of the diaphragm toward the pump chamber.
 5. The diaphragm pump according to claim 4, wherein the diaphragm case has a fixing surface for supporting the diaphragm at the outer peripheral portion thereof, the regulating surface being formed continuously with the fixing surface, the regulating surface having a second convex surface region for supporting the diaphragm at a portion of the second convex surface region adjacent to the outer peripheral portion of the diaphragm and a second concave surface region which is formed continuously with the second convex surface region for supporting the diaphragm at a portion of the second concave surface region adjacent to the center point of the diaphragm.
 6. The diaphragm pump according to claim 5, wherein curvatures of the second convex surface region and the second concave surface region of the regulating surface of the diaphragm case are the same.
 7. The diaphragm pump according to claim 6, wherein the second surface of the flange has a first concave surface region in addition to the first convex surface region, the first convex surface region of the second surface contacting the diaphragm at a portion of the first convex surface region adjacent to the fitting member, the first concave surface region of the second surface being formed continuously with the first convex surface region, the first concave surface region contacting the diaphragm at a portion of the first concave surface region adjacent to the outer peripheral portion of the diaphragm, curvatures of the first convex surface region and the first concave surface region of the second surface of the flange and the curvatures of the second convex surface region and the second concave surface region of the regulating surface being the same. 